Patent GB-475752-A (GB)
Title: Improvements in or relating to milling machines
IPC: B23C1/025
Filed: 1936-08-05
Abstract: 475,752. Milling-machines. HERRMANN, R. Aug. 5, 1936, No. 21516. [Class 83 (iii)] In a milling-machine, the spindle 1 has an orbital movement and is eccentrically mounted in a bearing sleeve 4 which is itself mounted eccentrically in a bearing member 7, the sleeve and the member 7 being relatively rotated to vary the radial position of the spindle by means of a reversible motor. In the application to thread milling, the rotation of the member 7 gives the orbital movement of the tool spindle around the stationary workpiece while the timed rotation of the sleeve 4 produces automatic radial movements of the tool to feed it into the work and withdraw it on completion of the cut. The member 7 is mounted in bearings 8, 9 in a headstock 10 movable longitudinally on guides 11. The spindle is driven by a motor 13 through gears 14, 15, the motor being secured to a casing 16 held against rotation by a roller 17 engaging in a slideway 18. The member 7 is rotated by worm gearing 19 driven from another motor 24 through gears 26, spindle 27, worm gears 28, shaft 29, and change gears 31. The sleeve 4 carries external teeth 34 engaging internal teeth on a loose ring 35, Fig. 3, which has external worm wheel teeth engaged by a worn: 36 on a shaft 37 driven from the motor 24 through gearing 39, so as to rotate the ring 35 synchronously with the member 7. The latter gear is loose on shaft 37 and may be clutched thereto by a coupling 41. The spindle 37 may be rotated by a hand wheel 42 to set the radia position of the cutter spindle. The spindle 37 is longitudinally movable to an extent limited by a groove 47 in its end bearing by means of a reversible electric motor 49 driving through gears 52 a shaft 51 operating rack teeth on the bearing. The applied voltage of the motor 49 may be maintained to hold the shaft 37 in either end position. The slide 10 is moved longitudinally by a lead screw 54 driven in unison with the member 7 to give the required lead to the thread. For this purpose a gear 59 on the member 7 is connected to the lead screw through gears 60, shaft 58 and change gears 56. By reversing the motor 24 the member 7 is rotated backwards by the amount of its forward motion in excess of one complete rotation and is then locked by a spring pin 70, Fig. 9, while the headstock is quickly returned by rotating the lead screw nut 64 from a motor 67, Fig. 9, through worm gearing 68. In order to bring the tool axially into the work at the start of an operation, the headstock slide 10 is moved by a reversible motor 73 which drives a crank 72 which moves the headstock to positions determined by a fixed stop 85 and stops 83, 84 on a transverse headstock slide 65. The crank drive is selflocking in the end positions. The machine cycle is shown diagrammatically in Fig. 12. The cutter starts at point O and is moved to position 1 by the crank mechanism. During this movement the spindle-driving motor is switched on and then the motor 24 for rotating the member 7 and the motor 49 for moving the tool radially outwards into the work into position II. The spindle then moves in a helical path for somewhat more than a complete revolution to complete the threading and reach position III. The motor 49 is then again switched on in the opposite direction to withdraw the tool to position IV. The motor 24 is then switched on in reverse and rotates through a fraction of a revolution to return the member 7 while the motor 67 returns the lead screw and the crank-driving motor 73 returns the tool to position O where all the motors are switched off. The various motors are controlled by switches arranged as shown in Fig. 13. The switches A, Z, U and R are mounted in switching apparatus K on the headstock and the switch H for the spindle drive is carried on the column 12. The shaft 87a, Fig. 9, carries the moving contacts 85 of the switch A while the shafts 87ur and 87z carry the contacts of the corresponding switches U, R and Z. The letters v and r denote contacts for forward and reverse running respectively. At the beginning of an operation, a hand lever 91 is operated to rotate switch shaft 87a, Fig. 9, and moves switch A to forward running position where it is locked against the urge of a spring 97. This operates the crank mechanism for the axial tool approach. At the end of this movement a dog 100 actuates a lever shaft 99 which acts on a lever arm 103, Fig. 14, to actuate shaft 87z and to move and lock switch Z in forward running position and give the radial movement. When the radial feed motor 49 runs in forward direction it rotates a locking disc 115 which shortly causes switch U to be locked in forward running position. Subsequently, the motors 49 and 24 are switched on for forward running and the spindle 1 is fed radially outwards until position II, Fig. 12, is reached, after which the member 7 revolves further until position III is reached. The switch shaft 87z is then automatically released and switch Z moves to reversing position r thereby causing motor 49 to withdraw the spindle radially inwards. Finally, the carriage is returned to initial position and all motors automatically switched off. The knee 139 carries the usual compound tables 142, 143. For circular milling operations a modified switch-gear is employed and is actuated by cams mounted on and operated by the rotation of the member 7.